7/29/2019 Lab 3 - Impact Test

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Lab 3Pendulum/Charpy Impact Test Mechanics and Properties of Materials

Dr. PJ McAllen Page 1 of 2

Lab 3 Pendulum Impact Test (Charpy Impact Test)

Name: ____________________

Student ID: ____________________

Programme: ____________________

Group: ____________________

The following worksheet is to be completed by each student and submitted at the start of the next lab session.

The impact tester will give a reading of an angle that the pointer reaches at its maximum height. Once we work

out the change in height (from the start position) we can find the change in energy, which is the amount of

energy absorbed by/used to break the specimen. When dividing this by the CSA (at notch), it will give us the

notched bar impact strength that can be used to compare different materials. The higher the a k value, the

greater the materials impact strength.

At low temperatures some metals that would be ductile at room temperature become brittle. This is known as a

ductile to brittle transition. The ductile to brittle transition temperature is strongly dependant on the

composition of the metal. Steel is the most commonly used metal that shows this behaviour.

For some steels the transition temperature can be around 0C, and in winter the temperature in some parts ofthe world can be below this. As a result, some steel structures are very likely to fail in winter.

The sinking of the titanic was caused primarily by the brittleness of the steel used to construct the hull of the

ship. In the icy water of the Atlantic, the steel was below the ductile to brittle transition temperature.

In these conditions even a small impact could have caused a large amount of damage. The impact of an iceberg

on the ship's hull resulted in brittle fracture of the bolts that were holding the steel plates together. Nowadays

engineers know more about this phenomenon and the composition of the steels used is much more controlled,

resulting in a lower temperature at which the ductile to brittle transition occurs.

7/29/2019 Lab 3 - Impact Test

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Lab 3Pendulum/Charpy Impact Test Mechanics and Properties of Materials

Dr. PJ McAllen Page 2 of 2

Question 1: The test specimens used in this test are manufactured to which standard? ______________

Question 2: The parameter describing the ability of a material to absorb energy is _________________

Question 3: Brittle fracture requires energy to separate atoms and expose new surfaces along the

fracture path. Ductile failure requires not only the energy just mentioned but much more additionalenergy to deform _____________ the material ahead of the fracture.

Question 4: One measure of the toughness is the area of the _______________________________

Question 5: The unit for toughness (product of stress and strain) is ________________

Question 6: A notch is machined in the side of the test specimen to serve as a ____________________,

ensuring that fracture will occur at that location.

Question 7: When designing a structure it is usually preferable for the material to fail in a ductile

manner as there will be _________________________________________________ before the finalfailure occurs.

Question 8: How did the material affect the swing of the arm?

Question 9: What was the fracture surface of the specimen like?

Question 10: Complete the following Table by determining the impact strength of the specimens

provided.

Test SpecimenStarting

Mass

(m)

Start Height(h1)

Start Angle()

Finish Angle()

EnergyAbsorbed

(Ak)

ImpactStrength

(ak)

Material & CSA Kg P1 (m) J J/m2

Brass (5.5x10-5

m2) 4 0.6386 148.32

Steel (5.5x10-

m ) 4 0.6386 148.32

Arm radius = 0.345 m

Specimens available:

Steel EN3B (BS970, 230M07) is a popular mild steel (not >0.25% carbon).

Brass CZ121 (BS2874). Brass, i.e. copper and zinc, can be either alpha (ductile and can be cold

worked, with zinc